Heat sink for an electrical device and method of manufacturing the same

ABSTRACT

A heat sink for an electrical device has a frame and at least one fin. The frame has an inner chamber. The fin is mounted in the inner chamber of the frame to separate the inner chamber of the frame into at least two channels. Therefore, heat generated from any electrical element connected to or mounted on the heat sink will transfer evenly to the heat sink. The heat sink not only dissipates heat evenly, but also provides multiple channels to dissipate heat by convection. Because the heat sink only has one frame, assembly of an electrical device is easy and quick.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to a heat sink used in electrical devices,and more particularly to a heat sink used in an un-interruptible powersupply (UPS), which is assembled easily and has excellent efficiency ofheat dissipation.

2. Description of the Related Art

Electrical devices, such as an un-interruptible power supply (UPS),require excess heat to be removed leading to the development of heatsinks.

Conventional methods of dealing with the excess heat are such asselecting low heat generating elements, enlarging the heat sink orincreasing the fans to remove the heat out of the device. Apparently,the methods have the disadvantage such as increasing the cost, enlargingthe size, and decreasing the performance. Each of said methods goesagainst the object of the high power density and miniaturization, so thebest method is improving the efficiency of the heat dissipation.

The heat sink of the electrical device is made of extruded aluminum andhas a surface area and fins that enlarge the surface area to reduce heatin the electrical device according to a basic overall heat-transferequation:

Q=UA _(t)(T _(ave) −T _(∞))

Wherein

-   -   Q is heat transfer rate;    -   U is overall heat transfer coefficient;    -   A is the surface area of the heat sink;    -   T_(ave) is an average temperature in a surface of the heat sink;    -   T_(∞) is a temperature of environment.

With reference to FIGS. 5 and 6, a UPS (1′) has a front panel, a rearpanel, a fan (20), a conventional heat sink (30) and electricalelements. The fan (20) is mounted on the rear of the UPS (1′). The heatsink (30) is mounted in the UPS (1′), and has two symmetrical frames(31). Each frame (31) is U-shaped, faces the other frame to form aparallelepiped with an inner chamber and has two sides and several fins(33).

The fins (33) are parallel extruded from the frame (31) and have twosurfaces that increase a surface area of the heat sink (30). Theelectrical elements are mounted onto the frame (31), to allow thegenerated heat to be easily transferred to the fins (33) and removed byconvection increased by the airflow forcing by the fan (20). Therefore,the generated heat can be removed out of the UPS (1′).

However, all of the electrical elements mounted on the two frames (31)do not be activated together. Because of the limitation of design,usually only the electrical elements on the same frame are activated inthe same time, it rises the temperature of the frame. But the otherframe keeps a low temperature comparatively, because of the electricalelements mounted on it aren't activated in the same time. As a result,the whole heat sink (30) hasn't a unit temperature, the other framecan't be used completely, so the total efficiency of the heatdissipation decreased.

To overcome the shortcomings, the present invention provides a heat sinkfor electrical device to mitigate or obviate the aforementioned.

SUMMARY OF THE INVENTION

The primary objective of the present invention is to provide a heat sinkused in an electrical device, which is assembled easily and has a highperformance to dissipate the excess heat.

To achieve the objective, the heat sink for an electrical device inaccordance with the present invention has a frame and at least one fin.The frame has an inner chamber. The fin is mounted in the inner chamberof the frame to separate the inner chamber of the frame into at leasttwo channels. Therefore, heat generated from any electrical elementmounted on the heat sink will transfer evenly to the heat sink of. Theheat sink not only spreads heat evenly, but also provides multiplechannels to dissipate the excess heat by convecting with the airflow.Besides, the heat sink only has one frame, so assemble the heat sinkwith the electrical device will be much easier and quicker.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objectives, advantages and novel features of the invention willbecome more apparent from the following detailed description of thepreferred embodiment of the invention illustrated in the accompanyingdrawings, wherein:

FIG. 1 is a perspective view of a heat sink in accordance with thepresent invention;

FIG. 2 is a front view of the heat sink in FIG. 1;

FIG. 3 is a perspective view of the heat sink in FIG. 1 mounted in anun-interruptible power supply;

FIG. 4 is a side view of the heat sink in FIG. 3;

FIG. 5 is a perspective view of a conventional heat sink in accordancewith the prior art; and

FIG. 6 is a perspective view of the conventional heat sink in FIG. 5mounted in an un-interruptible power supply.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIGS. 1 and 3, a heat sink (10) in accordance with thepresent invention is used in an electrical device (1) and has a frame(11) and at least one fin (12).

The frame (11) may be a parallelepiped, may be made of extruded aluminumand has an inner chamber. A rectangular frame (11) has a width of 62millimeters (mm), a height of 58 millimeters (mm), two mounting sides(14) and two non-mounting sides (15). The mounting sides (14) aredefined opposite to each other and may be 4.1 mm thick. The non-mountingsides (15) are defined opposite to each other, are perpendicular to themounting sides (14) and may be 2.3 mm thick.

With further reference to FIG. 2, the at least one fin (12) is mountedin the inner chamber of the frame (11) to separate the inner chamber ofthe frame (11) into at least two channels (13). When six fins (12) aremounted in the inner chamber, the fins (12) are mounted at intervals andeach interval is 6 mm thick. The at least one fin (12) may be aluminumextruded from the frame (11) and may be rectangular. Each rectangularfin (12) has two edges. The edges of the fin (12) connect respectivelyto the mounting sides (14) of the rectangular frame (11) to form atleast two channels (13). Each rectangular fin (12) is 1.9 mm thick.Preferably, six rectangular fins (12) are used. The channels (13) areformed in the frame (11).

With further reference to FIG. 3, the electrical device (1) may be anun-interruptible power supply (UPS) and has a front, a rear, the heatsink (10) of the present invention, at least one ventilating device, abracket (50) and a printed circuit board (PCB) (51).

The heat sink (10) is mounted on the PCB (51)

The at least one ventilating device (20) communicates with the channels(13) of the heat sink (10) and forces air to flow through the channels(13) of the heat sink (10) to increase the dissipation efficiency of theheat sink (10). The ventilating device (20) may be a fan. Theventilating device (20) is mounted on the rear of the UPS (1) and may bemounted on the frame (11) of the heat sink.

The bracket (50) is mounted between the front and rear and has twoconnecting edges and two surfaces. The connecting edges are respectivelyconnected to the front and rear of the UPS (1).

The PCB (51) is mounted to the bracket (50) and allows one of thenon-mounting sides (15) of the frame (11) to be mounted on the PCB (51).Therefore, the heat sink (10) can be mounted or easily connectedindirectly to the PCB. The PCB (51) comprises a first group ofelectrical elements and a second group of electrical elements.

With further reference to FIG. 4, the first group of the electricalelements is mounted on one mounting side (14) of the frame (11) of theheat sink (10) and has multiple DC/DC metal-oxide-semiconductorfield-effect transistors (DC/DC MOSFET) (41, 41 a) and a rectifier (42).The DC/DC MOSFETs (41, 41 a) are mounted on one mounting side (14) ofthe frame (11) of the heat sink (10) from the front to near the rear ofthe UPS (1), and the DC/DC MOSFET nearest the rear being the first DC/DCMOSFET (41 a). The rectifier (42) is mounted on the side of the frame(11) on which the DC/DC MOSFETs (41, 41 a) are mounted, is adjacent tothe first DC/DC MOSFET (41 a) at the rear of the UPS (1). The secondgroup of the electrical elements is mounted on the other mounting side(14) of the frame (11) of the heat sink (10) and has a first powerfactor correction diode (PFC diode) (43), a second PFC diode (44), afirst inverter insulated gate bipolar transistor (IGBT) (45) and asecond inverter IGBT (46). The first PFC diode (43), the second PFCdiode (44), the first inverter IGBT (45) and the second inverter IGBT(46) are respectively mounted on the frame (11) of the heat sink (10)from the front to the rear of the UPS (1).

While AC input power is normal, the UPS (1) will work in the Line Mode,the rectifier (42), the PFC diode (43), the second PFC diode (44), thefirst inverter IGBT (45) and the second inverter IGBT (46) will beactivated.

While AC input power is abnormal, the UPS (1) will use the backup DCpower and work in the Battery Mode, all the DC/DC MOSFETs (41, 41 a),the first inverter IGBT (45) and the second inverter IGBT (46) will beactivated.

Heat generated from any electrical elements will transfer evenly to theheat sink (10). The ventilating device increases airflow and the heatcan be dissipated quickly and efficiently.

A method of manufacturing the heat sink for the electrical device inaccordance with the present invention, comprises two steps:

a) step comprises making a frame which has an inner chamber, twomounting sides and two non-mounting sides. The mounting sides aredefined as opposite to each other and are used for mounting generatingheat electrical elements. The non-mounting sides are defined as oppositeto each other and at least one of them is used for fastening the heatsink to the electrical device.

b) step comprises mounting at least one fin in the inner chamber of theframe to separate the inner chamber of the frame into at least twochannels. Each fin has two edges that are connected respectively to thetwo mounting sides of the frame.

Examples: These experiments compare an efficiency of the heat sink (10)of the present invention with a conventional heat sink.

Test 1.

AC power is supplied to the UPS (1) at 170 volts until the electricalelements hold a steady temperature. Some electrical elements mounted onthe heat sink of the present and the conventional heat sink aremeasured, as shown in Table 1:

TABLE 1 Conventional Temperature Electrical heat sink Present inventiondifference element (T/° C.) (T/° C.) (T/° C.) PFC diode (43) 66.7 49.4−17.3 Second PFC diode (44) 67.2 54.3 −12.9 First inverter IGBT (45)75.1 63 −12.1 Second inverter IGBT 73 66.7 −6.3 (46) First DC/DC MOSFET52.1 50.3 −1.8 (41a) Rectifier (42) 64.9 69.4 +4.5

Text 2.

After test 1, DC power is supplied from a battery to the UPS (1) and theUPS work in Battery Mode for 30 minutes. The temperatures of some of theelectrical elements mounted on the heat sink of the present and theconventional heat sink are measured, as shown in Table 2:

TABLE 2 Conventional Temperature Electrical heat sink Present inventiondifference element (T/° C.) (T/° C.) (T/° C.) First DC/DC MOSFET 93.878.1 −15.7 (41a) Rectifier (42) 79.5 70.9 −8.6

Test 3.

After test 2, AC power is supplied to the UPS (1) at 272 volts.Temperatures of some electrical elements mounted on the heat sink of thepresent and the conventional heat sink are measured, as shown in Table3:

TABLE 3 Conventional Temperature Electrical heat sink Present inventiondifference element (T/° C.) (T/° C.) (T/° C.) PFC diode(43) 59.9 47.1−12.8 Second PFC diode (44) 60.6 51.4 −9.2 First inverter IGBT (45) 67.359.7 −7.6 Second inverter IGBT 65.1 61.4 −3.7 (46) First DC/DC MOSFET49.8 47.3 −2.5 (41a) Rectifier (42) 50.3 49.7 −0.6

According to the foregoing tables, the heat sink (10) of the presentinvention efficiently dissipates heat. Therefore, the heat sink (10) ofthe present invention not only transfers heat evenly, but also providesmultiple channels (13) to dissipate heat by convection. Additionally,because the heat sink (10) only has one frame (11), the heat sink (10)can reduces assembly time and difficulty of the electrical device (1).

Even though numerous characteristics and advantages of the presentinvention have been set forth in the foregoing description, togetherwith details of the structure and function of the invention, thedisclosure is illustrative only. Changes may be made in detail,especially in matters of shape, size and arrangement of parts within theprinciples of the invention to the full extent indicated by the broadgeneral meaning of the terms in which the appended claims are expressed.

1. A heat sink for an electrical device comprising a frame, having aninner chamber; two mounting sides being defined as opposite to eachother and being adapted to allow generating heat elements of theelectrical device to be mounted on the mounting sides; and twonon-mounting sides being defined as opposite to each other and at leastone of the non-mounting sides allowing the heat sink to be fastened tothe electrical device; at least one fin mounted in the inner chamber ofthe frame to separate the inner chamber of the frame into at least twochannels and each fin having two edges being connected respectively tothe two mounting sides of the frame.
 2. The heat sink for an electricaldevice as claimed in claim 1, wherein each fin is rectangular.
 3. Theheat sink for an electrical device as claimed in claim 2, wherein theframe is made of extruded aluminum; and the at least one fin is aluminumextruded from the frame.
 4. The heat sink for an electrical device asclaimed in claim 1, wherein said electrical device is an UPS.
 5. Amethod of manufacturing a heat sink for an electrical device comprisingsteps of: a) making a frame which has an inner chamber; two mountingsides being defined as opposite to each other and being used formounting generating heat electrical elements; and two non-mounting sidesbeing defined as opposite to each other and at least one of them beingused for fastening the heat sink to the electrical device; and b)mounting at least one fin in the inner chamber of the frame to separatethe inner chamber of the frame into at least two channels and each finhaving two edges being connected respectively to the two mounting sidesof the frame.
 6. The method of claim 5, wherein the frame is aparallelepiped.
 7. The method of claim 5, wherein each fin isrectangular.
 8. The method of claim 6, wherein each fin is parallel withthe two non-mounting sides of the frame.
 9. The method of claim 5,wherein the frame is made of extruded aluminum; and the at least one finis aluminum extruded from the frame.